Continuing efforts to improve the safety and efficiency with which chain saws may be operated have produced a variety of chain saw safety mechanisms. Many such mechanisms are designed to avert the movement of a chain saw cutter chain in response to adverse or potentially dangerous operating conditions.
Such conditions may entail abrupt or uncontrolled chain saw movements occur, such as "kick-backs", or operations where an operator's hand slips off of the supporting handle structure of a chain saw.
Many chain saw safety devices intended to avert cutter chain movement depend upon operator manipulation of chain saw safety components such as "dead man" handles or switches, or safety bars or handles in order to effect actuation of cutter chain stopping devices. Representative disclosures of such chain saw operator manipulated safety devices include:
Country Patentee No./Date ______________________________________ United States Irgens 3,361,165/Jan. 2, 1968 United States Mattson et al 3,664,390/May 23, 1972 United States Moore 3,739,475/June 19, 1973 United States Gustafsson 3,776,331/Dec. 4, 1973 United States Johansson 3,785,465/Jan. 15, 1974 United States Johansson 3,807,538/Apr. 30, 1974 Sweden Westerlund 359170/Mar. 18, 1970 ______________________________________
Chain saw devices, characterized by inertia device actuated safety brakes and which are not dependent upon operator manipulation, are set forth in the following disclosures:
Country Patentee No./Patent Date ______________________________________ United States Wilkin 3,485,326/Dec. 23, 1969 United States Gudmundsen 3,485,327/Dec. 23, 1969 United States Johansson 3,785,465/Jan. 15, 1974 ______________________________________
Other chain saw safety mechanisms are featured in other issued patents and pending applications, some of which are assigned to the assignee of the present invention.
The present invention, believed to advance the chain saw safety mechanism art, departs significantly from prior art teachings such as those noted above.
The present invention is multifaceted in nature and is believed to achieve significant improvements with respect to the development of a reliable and rapidly responding chain saw mechanism, making effective use of chain saw-generated energy as the safety device-actuating means.
Moreover, these advantages are achieved without having to significantly or drastically alter conventional chain saw structure and without materially or significantly increasing overall chain saw size.
The advance in the art entailed in the present invention involves three independently viable concepts, usable separately or in combination in chain saw safety devices and chain saw safety techniques.
A first independently significant facet of the invention resides in a method and apparatus characterized by the use of chain saw-developed and stored energy which is employed to de-activate or disable a continuously operable safety mechanism while normal cutting operations take place. This technique insures continuous availability of the operating effect of the chain saw safety device, and insures that the chain saw will be operable for normal cutting operations only when the safety mechanism-actuating energy source has in fact been developed and stored.
The second independently significant facet of the invention involves a method and apparatus wherein an inertia mechanism, independent of operator manipulation, is operable in response to adverse conditions such as a chain saw kick-back, to trigger the release of chain saw-generated and stored energy for the purpose of actuating a safety mechanism.
A third independently significant facet of the invention entails the use of a chain saw engine to develop a body of pressurized fluid, with this pressurized fluid body being stored and utilized to actuate a safety mechanism.
These independently significant facets of the invention are practiced in a common method and apparatus context wherein a movement-arresting means is provided which is operable to arrest the movement of cutter chain of a chain saw. A chain saw engine-actuated, energy-developing and storing means is also provided, which is operable to:
develop cutter chain movement-controlling energy during, and in response to, operation of the engine of the chain saw and PA1 store this developed energy for subsequent use in actuating the movement-arresting means.
This basic or common context of the invention further entails the provision of movement-control means operable to release the stored, chain saw engine-developed energy. In response to this energy release, the movement-control means is operable to cause motion-arresting force to be imparted to the movement-arresting means.
In this common context of the independently significant aspects of the invention, there is also provided chain saw condition-responsive means. This latter means is operable, in response to a condition of the chain saw adverse to the safety of the operator, to actuate the movement-control means and cause the movement-control means to release the developed energy and cause the motion-arresting force to be imparted to the motion-arresting means.
In the first independently significant facet of the invention, above noted, the chain saw engine-actuated, energy-developing and storing means is operable to apply the stored, chain saw engine-developed energy to the movement-arresting means to prevent its actuation. This disabling actuation, in this aspect of the invention, continues until operation of the movement-control means, in response to actuation by the chain saw condition responsive means, is operable to release the engine-developed energy.
Thus, this aspect of the invention, i.e., the first independently significant facet, deals with a safety mechanism where a cutter chain movement arresting device is disabled only when control energy has been developed and stored by the chain saw and applied to the movement-arresting means of the safety mechanism. When the energy has either been not developed or has been released, the movement-arresting means is automatically operated.
In the secondly independently significant aspect of the invention, the chain saw condition-responsive means constitutes inertia-responsive means independent of chain saw operator manipulation. Such inertia-responsive means is operable in response to a kick-back of the chain saw to actuate the movement-control means so as to release the developed and stored energy and cause the motion-arresting force to be imparted to the motion-arresting means.
Thus, this second independently significant facet of the invention is directed to the use of an inertia mechanism -- independent of chain saw operator manipulation -- which serves to trigger the release of chain saw engine-developed and stored energy for the purpose of actuating a chain saw cutter chain movement-arresting device.
The third independently significant facet of the invention, which like the other two facets, is incorporated in the common contextual setting above discussed, involves the development and storing of cutter chain movement-controlling energy in the form of pressurized fluid.
Thus, this third aspect of the invention entails a unique and specific energy-development and storage technique where the development, storing and release of pressurized fluid governs the operation of a safety mechanism.
Advantageously, the three independently significant facets of the invention may be combined in a composite, fourth concept so as to entail and employ the advantages of each of the three individual invention facets above noted.
A fifth aspect of the invention entails a preferred embodiment arising out of the fourth composite invention concept above noted.
This fifth aspect of the invention is characterized by a rotary inertia mechanism which serves to control the operation of a valve mechanism effecting the containing of the above-noted pressurized fluid. When the rotary inertia mechanism effects opening of the valve, and thereby release of the pressurized fluid, the energy of the heretofore stored pressurized fluid is dissipated so as to remove a brake-disabling, pressure influence acting on a brake-controlling diaphragm means.
In a sixth aspect of the invention, until the pressurized fluid attains a pressure in excess of that which can be developed by the engine operating at idle speed or below, the diaphragm means is unable to disable the braking mechanism, and the cutter chain remains substantially immobile.
In describing the invention by way of example, but not by way of limitation, reference will be made to a preferred embodiment illustrated in drawings appended to this specification.